UNIX for Advanced & Expert Users

On a 2.6.21 kernel (MontaVista, x86_pentium4), I'm failing to see expected "core.pid" files dropped.

Consider this tiny program, "dumpcore.c":

#include <stdio.h>
#include <stdlib.h>
#include <sys/prctl.h>

int main( int argc, char ** argv )
{
printf("dumpable = %d\n", prctl( PR_GET_DUMPABLE, 0, 0, 0, 0 ) );
abort();
}

Build command is equally simple:

$ gcc -m32 -g -o dumpcore32 dumpcore.c

If I ssh into the MV system, login as root, and execute the program, I see a core file generated as expected:

$ ssh root@W.X.Y.Z
Last login: Fri Mar 21 22:04:03 2008 from W.X.Y.Q
root:/# /home/klittle/dumpcore32
dumpable = 1
Aborted (core dumped)
root:/# ls -la /disk/core
total 72
drwxrwxrwx 2 root root 4096 Mar 21 22:23 .
drwxrwxrwx 11 root root 4096 Mar 4 16:10 ..
-rw------- 1 root root 143360 Mar 21 22:23 dumpcore32.3314.1206138192.

But, if I "oneshot" the command by giving it on the ssh command line:

$ ssh -t -t root@W.X.Y.Z "/home/klittle/dumpcore32;ls -la /disk/core"

dumpable = 1
bash: line 1: 3344 Aborted /home/klittle/dumpcore32
total 8
drwxrwxrwx 2 root root 4096 Mar 21 22:24 .
drwxrwxrwx 11 root root 4096 Mar 4 16:10 ..
Connection to W.X.Y.Z closed.

The core file is nowhere to be found.

ulimit in both cases is "unlimited" (I double checked). Anyone have any insight here?

TIA,
-k

Strange, the ssh syntax is correct, i.e. putting " ; " around two command will work, you can try simpler commands, such as "echo string > file" and then list the file, or "touch". I think the problem may be in the interactive invocation of the coredump binary.

Oh, the syntax is fine -- the original problem was discovered in a case where there were five or six shell commands strung together with ';'. All the commands execute. The only issue is the missing core file that is expected when "dumpcore32" is invoked.
Interactive? All there is is output to stdout. If I remove that one printf(), the same thing happens: core file if I run the command while in a shell on the target system, no core file if I use "ssh .... <command>".

Weird...

What were the other 5 or 6 commands I wonder and what order of invocation?
fwiw I can't replicate your issue.

The other commands were a "cd" to a specific location, the setting of some environment variables, then invocation of a large in-development app with a primitive debug shell, one command of which caused a call to abort() (ABORT(3)). It's a moot issue, I think, since the very simple example above is showing the exact same (and strange!) behavior as regards a core file being generated or not.

-k

All I would suggest is the output of ulimit -a (or the like) between commands and then an explicit dump of environment to log in any compiled binaries. The abort() call is interesting as :

Code:

If the abort() function causes program termination, all open streams are closed and flushed.

What that means in context is TBD.